一种低含氟磷酸盐二倍频激光色分离玻璃及其制备方法

本发明属激光玻璃材料技术领域，具体涉及一种低含氟磷酸盐二倍频激光色分离玻璃及其制备方法。该玻璃的原料成分为：1.5?10％的Li2O，0?8％的Na2O，0?15％的K2O，1.5?10％的MgO，0?5％的CaO，0?2％的SrO，1?6％的BaO，1?9％的Al2O3，2?10％的ZnO，55?75％的P2O5，1?2％的YF3，0.5?2％的LaF3，0.1?2％的Co3O4；各原料的成分配比为摩尔质量分数。本发明解决了氟化物玻璃及高含氟玻璃体系的易析晶、成玻性差、挥发大、难以均化消除条纹以及粘度小造成的大尺寸成型困难等问题。同等测试条件下，其激光损伤阈值明显高于熔石英玻璃材料，可代替熔石英玻璃材料用于高能高功率激光器中提高系统的激光负载能力。</p

Multi-component yttrium aluminosilicate (YAS) fiber prepared by melt-in-tube method for stable single-frequency laser

The multi-component glass fibers have demonstrated their unique advantages in the application of single-frequency lasers due to their higher solubility of rare-earth ions and thus a higher gain per unit length in a compact fiber laser cavity. In this study, multi-component yttrium aluminosilicate (YAS) fiber with high doping concentration of Yb3+ was prepared by the &quot;melt-in-tube&quot; (MIT) method. A unit-length gain of 3 dB/cm was obtained in a 4.4 cm-long YAS fiber, the laser output slope efficiency reached 23.8% in a 10 cm-long Yb:YAS fiber. Single-frequency laser operation was achieved in a 1.7-cm-long Yb:YAS active fiber. To the best of our knowledge, this is the first demonstration of single-frequency laser with this YAS glass fiber as gain medium. The novel multi-component YAS fiber can be applied as a new gain material to realize single-frequency fiber laser.</p

Effect of refractive index measurement error on immersion grating spectral lines

Firstly, the effect of refractive index changes on spectral line spacing is calculated and analyzed. Because refractive index changes with wavelength-variety, theoretically, the 0.5 nm interval should be separated by 5 pixels. The spectral distribution will drift with considering the changes in refractive index. At the same time, the inversed spectral line drift caused by measurement errors(&plusmn;1&times;10-3?1/4?&plusmn;1&times;10-4?1/4?&plusmn;1&times;10-5) are analyzed. The same refractive index error, the effect on long waves is greater than short waves. When the refractive index is positive, the spectral line drifts in the negative direction. When the refractive index is negative, the spectral lines drift in the positive direction, and the positive and negative drift are basically symmetrical. When the accuracy error of refractive index measurement is &plusmn;1&times;10-4, the spectral line drift is 0.7 pixels. When the error increases or decreases by an order of magnitude, the number of drift elements also increases or decreases by the same order of magnitude. &copy; 2019 SPIE.</p

A chiral long-period grating fabrication method based on axis-offset rotating optical fiber

We propose a method to fabricate chiral long-period grating (CLPG) by rotating the standard single mode fiber which is fixed on two fiber holders but with an axis-offset. We show that, compared with traditional fabrication methods, this axis-offset method is capable of obtaining identical resonance wavelengths of the CLPGs for the same grating period. We investigate the performance of CLPGs by detecting the interference between the light emerging from CLPGs and a reference light. The achieved forklike and spiral interference patterns both confirm the generation of +/- 1-order optical vortex through CLPG. Experimental results indicate that high-quality CLPGs can be easily and repeatedly fabricated by this method.</p

Silicon drift detector applied to X-ray pulsar navigation

In this paper, a focused detection system for X-ray pulsar-based Navigation (XNAV) is designed based on Silicon Drift Detector (SDD). The detector electronics mainly adopts the digital trapezoidal shaping method to measure the Times-Of-Arrival (TOAs) and energy of photons. The time measurement accuracy is better than 500ns. The energy resolution is 191eV at 8.05keV, and the maximum count rate is 500kcps between 1 and 12keV. In the semi-physical simulation experiment, the filtering of noise photons by energy discrimination significantly improves the correlation degree between the cumulative pulse profile and the standard profile.</p

Simultaneous super-resolution reconstruction based on plane array staring remote sensing images

遥感面阵凝视成像系统可以得到同一场景的多幅图像,研究者常利用这一特点进行多幅图像超分辨重建,以提高遥感图像空间分辨率。但是这类研究往往将超分辨过程独立出来,很少结合成像系统的几何参数优化超分辨重建模型。因此,对成像姿态影响图像不同方向上分辨率的问题进行了分析,提出了基于姿态角的各向异性模糊估计,使退化模型更加准确。同时,为了进一步精确面阵凝视成像系统超分辨重建中的匹配参数估计,提高由系统引起的全局初始匹配误差的包容性,基于最大后验法提出并行优化超分辨率图像和匹配参数的方法。算法充分利用成像过程信息并实时优化匹配参数,实验结果证明与现有方法相比,不仅可以得到细节信息更丰富,更易于人眼观察的遥感图像,并且均方误差降低0.3倍左右,信息熵平均提高1.2。&nbsp;</p

Imaging property analysis of segmented mirror

拼接误差对拼接镜的成像性能有着重要的影响。基于标量衍射理论推导了单块子镜反射波的复振幅分布,并使用坐标变换法处理不同子镜间的拼接误差,建立了拼接误差对拼接镜成像性能影响的分析模型。数值仿真给出不同拼接误差下的点扩散函数以及对应的斯特列尔比曲线。结果表明,子镜沿z轴的平移误差对应的斯特列尔比曲线存在周期性变化。子镜倾斜误差和沿x,y轴平移误差对应的斯特列尔比曲线有着相同的结构。得到的结论为拼接镜成像质量分析提供了依据。&nbsp;</p

Truncated Gaussian-Bessel beams for short-pulse processing of small-aspect-ratio micro-channels in dielectrics

In order to control the length of micro-channels ablated at the surface of dielectrics, we use annular filtering apertures for tailoring the depth of focus of micrometric Gaussian-Bessel beams. We identify experimentally and numerically the appropriate beam truncation that promotes a smooth axial distribution of intensity with a small elongation, suitable for processing micro-channels of small aspect ratio. Single-shot channel fabrication is demonstrated on the front surface of a fused silica sample, with sub-micron diameter, high-quality opening, and depth of few micrometers, using 1 ps low-energy (&lt; 0.45 mu J) pulse. Finally, we realize 10 x 10 matrices of densely packed channels with aspect ratio similar to 5 and a spatial period down to 1.5 mu m, as a prospective demonstration of direct laser fabrication of 2D photonic-crystal structures. (C) 2019 Optical Society of America under the terms of the OSA Open Access Publishing Agreement</p

Underwater polarimetric imaging for visibility enhancement utilizing active unpolarized illumination

Underwater imaging is attractive but challenging. Images could be severely degraded by the particles in turbid water because of backscatter generation and signal light attenuation. In this paper, we focus on the scheme of underwater imaging and study the methods of visibility enhancement of turbid underwater images based on polarimetric imaging utilizing active unpolarized illumination. Compared with traditional polarimetric imaging using linearly polarized illumination, using unpolarized illumination ensures the polarization effect of the signal light could be neglected, no matter the depolarization degree of the object is high or low, which expands the application range of underwater polarimetric imaging and makes the underwater polarimetric imaging scheme more reliable and robust. Experimentally, the visibility and the contrast of underwater images are enhanced effectively. In addition, it is demonstrated that our method is applicable for objects of different materials and different imaging distances in turbid water. The contrast of underwater images could be promoted at least 100%, meaning that this kind of technique can be potentially used in many underwater environments.</p

Separation of optical angular momentum flux

We present an approach to separating the angular momentum (AM) flux of monochromatic light into its spin and orbital parts based on a symmetrized AM tensor &lt;(M) over bar &gt;. When considering the AM flux for a light beam through its cross section and that for an outgoing wave through a spherical surface in the far-field zone, the separation gives the desired results: the spin/orbital AM flux equals the integral of spin/orbital AM density times some weighting factor accounting for energy flux. When applied to Bessel beams, the obtained spin and orbital AM fluxes are exactly the same as those given by the paper (2014 New J. Phys. 16 093037) based on the canonical AM tensor separation. Furthermore, from the spin AM flux integral, the divergence-free spin AM tensor &lt;(S) over bar &gt; can be identified. We define the orbital AM tensor to be the difference between the total AM tensor &lt;(M) over bar &gt; and &lt;(S) over bar &gt;. Since &lt;(M) over bar &gt; is divergence-free, the integral for either spin and orbital AM flux, can be made on any closed surface.</p